Battery charger

ABSTRACT

The invention relates to a battery charger comprising a primary circuit; a secondary circuit consisting of at least one transformer secondary and a rectifier; and an overload prevention circuit. According to the invention, the primary circuit is provided with at least one general switch ( 5 ), a switch ( 6   b ) that is actuated by a relay ( 6   a ) in accordance with determined load conditions and a transformer primary, all of which are disposed in series. The overload prevention circuit comprises a voltage-sensitive switch and at least one reactance ( 7, 7   a,    7   b,    7   c,    7   d ) is disposed in the primary circuit or between the transformer and the rectifier in the secondary circuit. The invention is suitable for producing battery chargers.

[0001] This invention refers to a battery charger whose design allows great charging efficiency and an astounding charging speed to be obtained.

[0002] Specifically, the charger designed in this invention is meant for charging family vehicles, industrial vehicles or industrial machinery.

[0003] There are already well-known chargers which have an input for power supply from the mains, a transformer to transform the current voltage to the right voltage, a rectifier to convert the alternating input current into full-wave direct current and an overcharge prevention circuit, so that when the battery gradually gets up to the charging voltage, the circuit for preventing overcharges allows current through.

[0004] Though this type of chargers is reliable, they do on the other hand involve some adverse effects, that is, as the overcharge prevention circuit is activated, there is unnecessary power consumption (the current consumed going through said overcharge prevention circuit) and also as said circuit is activated, the charging current is lower, as it is shared with said circuit. The greater the battery charge, the lower the amount of current that goes through the charging circuit and the higher the amount through the overcharge prevention circuit.

[0005] This invention covers a charger for batteries which makes use of all the voltage as a charging voltage, so that control of overcharging is performed by means of a voltage control on charging terminals.

[0006] Batteries have been seen to offer greater resistance to charge the more discharged they are, due to the ionisation state of the products contained inside them. On the other hand, it has also been seen that although the battery offers a voltage opposed to the charging voltage, the “charging pressure” supplied by a charger connected to the mains or to a high power generator gives a voltage between terminals more dependent on said resistance than that of the opposition voltage.

[0007] This voltage does not act wholly against the charging voltage, so that the greater the state of charge of the battery the lower the resistance offered to said charge, and thus the greater the circulation of current through said battery, and consequently the greater the voltage between terminals.

[0008] It is consequently possible to find out the battery's charge status from the voltage found on the charge clips. Nevertheless, the antecedents existing have a device for preventing overcharging which absorbs a large amount of current, the greater the more fully-charged the battery is, so that while maintaining the consumption of the circuit, the charging circuit strictly speaking receives an amount of current tending to zero.

[0009] Another effect found with batteries is the stabilisation of the voltage after the charge has been deactivated, there being a certain drop in respect of the voltage as soon as said charging is completed. This drop is practically constant for a certain type of batteries, and is somewhere between 1V and 3V on a 12V battery, and approximately proportionate in batteries with greater voltage (always depending on the specifications of the battery in question). Therefore to get full charge, it is advisable for the battery to be charged at a voltage slightly over the nominal one, so that after stabilisation the voltage will actually be the nominal level.

[0010] It is also desirable for the charging terminals not to have any voltage whatsoever until reaching the charging position, even when the charging order has been given by activating the circuit.

[0011] It is also desirable for a charger to allow more than one type of battery (a particular voltage) and different powers to be charged. It is furthermore desirable to know the status of the charging operation, that is, which parts are active.

[0012] In order to illustrate the explanation that is to follow, we enclose with this descriptive report a sheet of drawings that represents the essence of this invention in two figures, and in which:

[0013]FIG. 1 shows the circuit of a charger in accordance with the invention, as in a first embodiment, and

[0014]FIG. 2 shows a simplified circuit in accordance with a second embodiment.

[0015] As seen in the embodiment shown in FIG. 1, 1 shows the connection terminals to the mains in alternating current, and 2 the charge terminals, where 3 is a transformer of suitable power, 4 a rectifier, such as a diode rectifier bridge and 5 a main power switch.

[0016] The charger basically has two circuits, a primary one or input circuit in alternating current and a secondary one, in which there is also alternating current at the output of the transformer, but this is immediately rectified by means of a rectifier, this rectified current or charge current acting in series with the battery. As an overcharge prevention circuit there is a voltage-sensitive switch, so that when the voltage reaches a certain value, the circuit is deactivated.

[0017] In accordance with the embodiment in FIG. 2, the primary circuit includes an alternating current input 1, a reactance 7 of a certain power, a switch 5 and an input phase in a transformer 3. The reactance 7 could nevertheless be in the alternating current part of the secondary circuit, that is, between the transformer and the rectifier.

[0018] The secondary circuit includes an output of the transformer 3, a rectifier 4 from which alternating current comes out, and charging terminals 2.

[0019] The rectifier (which has not been considered as needing to be represented in detail through involving a well-known technique) is preferentially formed (as is customary) by a set of diodes which allow and force the positive current through only one of the branches, while they allow and force the negative current through the other.

[0020] As an overcharge prevention circuit there is a voltage-sensitive switch 8 so that through the envisaged effect, when the voltage reaches a certain value, the switch closes, acting against a relay 6 a, which acts against a switch 6 b which opens the circuit, totally interrupting the charge and preventing any unnecessary consumption.

[0021] The circuit shown in FIG. 1 essentially includes the same diagram as FIG. 2, but in the latter there are further items.

[0022] The primary circuit according to said embodiment includes a series layout comprising a main switch 5 and a corresponding LED 16 which comes on when said switch closes the circuit, a fuse 9, reactances 7 a, 7 b, 7 c, 7 d, with their corresponding operating LEDs 15 a, 15 b, 15 c, which will operate alternately and a selector switch 19 which will determine which of the input lines will be active in respect of the output line which closes the circuit.

[0023] Said primary circuit also has a switch 6 b activated by a corresponding relay 6 a, which will be closed when there are charging conditions and will open when these conditions are no longer present.

[0024] The secondary circuit according to this embodiment consists of a circuit in which the secondary coil of transformer 3, a rectifier 4 and the charge terminals 2 are set in series.

[0025] To give the user more information about the charging status and conditions an ammeter, (set in series on one of the output branches) and a voltmeter (located in parallel between both output branches) have been included.

[0026] As an overcharging-preventing circuit, as in the embodiment shown in FIG. 2, there is also a switch 8 sensitive to voltage so that, through the effect foreseen, the switch closes when the voltage reaches a certain value, acting against a relay 6 a, which acts on a switch 6 b that opens the circuit, totally interrupting the charge and avoiding any unnecessary consumption.

[0027] As we shall see, a second voltage-sensitive switch 11 has been set in parallel with said overcharge prevention circuit, and said switch can be connected or disconnected by means of the manual switch 12 series connected to this. Said second switch 11 sensitive to voltage has the purpose of activating the start of the charging process when the battery located in a fixed machine (permanently connected to the charger) drops to a charge level lower than what is determined by said switch 11. In the event of said switch 11 being activated, a LED to indicate this can be fitted.

[0028] For the switch 6 b to be able to be activated by the relay 6 a, the contact 8 switch must be getting current from the battery, so that no current goes through unless the battery is connected. Nevertheless, when totally discharged batteries are connected, said contact switch 8 cannot be activated by means of the voltage from the battery, meaning that manual activation (or bridging) of the contract relay 6 b has to be made for the circuit to be activated.

[0029] For this purpose the switch 13, normally with a pushbutton or timer, has been included, to allow current through the switch 6 b even when the switches sensitive to voltage 8 and 11 are closed.

[0030] The charger being described means that not only can the charging be optimised through being done in series with the battery on charge, but this can be improved in time and quantity, due to the fact that this circuit allows charging with a voltage of roughly double the nominal battery voltage without there being any deterioration nor significant heating up.

[0031] The LEDS, insofar as they do not have an influence on the charging status, but only on the display for giving information to the user, are defined in a totally optional way.

[0032] Furthermore two or more components can be grouped in a printed or integrated circuit without this entailing any variation in the resources nor forfeiting the purposes described herein.

[0033] The invention is for industrial application in manufacturing battery chargers. 

1. A battery charger, consisting of a primary circuit, a secondary circuit formed at least of a secondary transformer coil and a rectifier and an overcharge prevention circuit, characterised in that the primary circuit has at least the following items set out in series: a main power switch (5), a switch (6 b) activated by a relay (6 a) in accordance with specific charge conditions, and a primary coil of a transformer, at least one reactance (7, 7 a, 7 b, 7 c, 7 d) is fitted in the primary circuit or between the transformer and the rectifier in the secondary circuit, being the reactance the element which imposes the current intensity of the circuit and also characterised in that the circuit for overcharge prevention consists of a switch sensitive to voltage, which also has a circuit for activating the start of the loading process for fully discharged batteries, with a switch (13) which activates the relay (6 b) of the primary coil or is set in parallel with this for putting it temporarily out of service.
 2. A battery charger, in accordance with claim 1, characterised in that the primary circuit has one or more reactances (7, 7 a 7 b) or sets of reactances (7 c, 7 d) that can be selected by means of a selector switch (9), so that when the circuit is closed through a reactance (7, 7 a, 7 b) or a set of reactances (7 c, 7 d) the other reactances or sets or reactances are deactivated, with said reactances determining the intensity of current which goes through the primary coil of a transformer (3) and consequently the battery charge current.
 3. A battery charger, in accordance with claims 1 and 2, characterised in that the overcharge prevention circuit consists of a switch sensitive to voltage (8) which connects or disconnects depending on the voltage existing at the charge terminals (2) so that when a specific pre-set voltage is reached the switch disconnects itself (or is disconnected) and acts on the relay (6 a) which disconnects (or connects) the primary coil switch (6 b).
 4. A battery charger, in accordance with claims 1 to 3, characterised in that it also has an automatic recharging circuit for static batteries when their charge drops below a pre-set value, consisting of a switch sensitive to voltage which connects or disconnects depending on the voltage existing between the charge terminals (2) so that when the voltage drops beyond a pre-set value the switch connects (or disconnects) and acts on the relay (6 a) which connects the switch (6 b) of the primary coil.
 5. A battery charger, in accordance with claim 1, characterised in that the circuit for activating the primary circuit activates a temporised switch that is disconnected in a pre-set time, when the battery has obtained a state with sufficient charge to activate the charge switch (8). 